In data collection and analysis, it is often essential that the information be displayed in a two dimensional (2-D) graphical representation. In such a 2-D representation, each datum is represented by a point (t,u). By displaying each point in the data, a graphical image is created.
When printing or displaying a graph of electronic data, the smallest element of resolution, termed a pixel, limits the overall resolution of the output. For example, on a 300 dot per inch (DPI) printer using an 11 inch by 17 inch sheet of paper, the output resolution for the graph could not exceed 3300 by 5100 pixels. Using a video display, one is more likely to achieve viewable areas of 1000 pixels by 1000 pixels. For electronic data with tens of thousands, or even hundreds of thousands of points, it is likely that more than one point will fall within a column one pixel in width.
Some systems such as flight recorders acquire large quantities of electronic data for analysis. One means of analyzing such electronic data is through a graph. In this instance, there exists a physical limitation on the resolution of the graph when electronically produced. Often, the resolution of an available output device is lower than that of the electronic data. Thus, displaying the graph requires some loss of resolution.
Often an entire quantity of electronic data is sent to an output device regardless of a large difference in the resolution of the data and the resolution of the output device. The electronic data is then displayed point by point. Of course, for large quantities of electronic data, it is time consuming to display a graph in this manner. Furthermore, it is likely that the same one pixel will be displayed or printed for each of a number of points. As the smallest element of resolution, a pixel can only be "on" or not "on", therefore, two or more operations displaying or printing the same pixel should have the same result as one such operation.
In the past, two dimensional graphs with axes t and u were electronically displayed by sending an entire quantity of electronic data comprising a plurality of points to an output device where the electronic data was displayed point by point. As the output resolution was often lower than that of the data, in order to display the data it was quantized to reflect values that were capable of being displayed.
One such method of quantization involved assigning to each pixel a range of values for t and u such that a point falling within the range of values for the pixel would print that pixel or display that pixel. For large quantities of data, this often resulted in repetition where two points fell within the range of the identical pixel. Further, for very large electronic data collections, this consumed both time and bandwidth.
In order to reduce the time and bandwidth required to print or display the graph, it is known in the art to sample the electronic data at predetermined intervals, thereby reducing the overall number of points sent to an output device. However, reducing the overall number of points through sampling can result in an inaccurate graphical representation of the original electronic data.
It is therefore an object of the current invention to provide a method of reducing the quantity of electronic data transmitted to an output device for producing a two dimensional graph on said output.